Walmart

Résumé

Walmart est une multinationale américaine spécialisée dans la grande distribution, fondée par Sam Walton. Lancée en 1962, l'entreprise s'est développée en Arkansas, avant de dominer le marché américain et commencer à s'internationaliser en 1991. Aujourd’hui, Walmart est le 1er groupe mondial de la grande distribution. En 2022, son chiffre d'affaires dépasse les 600 milliards de dollars, ce qui en fait la première entreprise mondiale en chiffre d'affaires, dépassant Exxon ou Saudi Aramco. Avec 2,1 millions de salariés travaillant dans 11 000 magasins, Walmart est le premier employeur privé au monde. Le groupe tire 80 % de son chiffre d'affaires des États-Unis. À l'étranger, ses premiers marchés sont le Mexique (2 634), l'Amérique Centrale (855 magasins), la Chine (434 magasins) et le Canada (408 magasins). Certaines de ses tentatives de développement, notamment au Japon ou en Allemagne, ont échoué, parfois pour des raisons culturelles. Symbole du capitalisme américain et de ses dér

Source officielle

https://fr.wikipedia.org/wiki/Walmart

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The aim of this course is to expose EPFL bachelor students to some of the main areas in financial economics. The course will be organized around six themes. Students will obtain both practical insights through real-world examples and understand how one can model the main economic trade-offs.

Le but du cours de physique générale est de donner à l'étudiant.e les notions de base nécessaires à la compréhension des phénomènes physiques. L'objectif est atteint lorsque l'étudiant.e est capable de prévoir quantitativement les conséquences de ces phénomènes avec des outils théoriques appropriés.

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Séances de cours associées (27)

Séances de cours associées

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Analysis of the Pigment Cell Specific Gene MART-1/Melan-A/mlana

Iraz Toprak Aydin

Pigmentation is a complex process that provides many diverse benefits for the organism. Pigment production takes place in the pigment cell lineage in dedicated organelles called melanosomes. Several proteins are specifically recruited to melanosomes for this purpose, and many of them are involved in melanin synthesis. MART-1 is one of the melanosomal proteins. It has been widely studied as an agent for immunotherapy against malignant melanoma but very little is known about the gene and its function. Here, I used different approaches in order to understand the biology of this pigment cell specific gene. First, I analyzed transcriptional regulation of the mouse MART-1 gene. I found that the shortest promoter region (0.6kb) alone is not sufficient to drive the expected MART-1 expression in vivo, even though it was able to express a luciferase reporter in vitro, in transfected cells. The largest promoter region (6.0kb) was able to produce expression of a LacZ reporter gene in the RPE layer starting from the early stages of embryogenesis. However it failed to drive melanoblast-specific expression in embryos and, only after birth, reporter gene expression in melanocytes became visible, indicating that distal regulatory elements might be involved in melanocyte/melanoblastspecific MART-1 expression. In order to visualize the spatial and temporal expression pattern of MART-1, I developed a MART-1::LacZ BAC reporter mouse and showed that in mouse, MART-1 expression starts at around E11.5-12.5, and its expression is exclusive to melanocytes and RPE. To understand the function of MART-1, I developed a knockout mouse model. I have shown for the first time that MART-1 is directly involved in pigmentation and that its loss leads to coat color dilution. It has been reported that MART-1 might be involved in trafficking and processing of the melanosomal proteins Pmel17 and OA1. I analyzed the distribution of Pmel17 and OA1, as well as other melanosomal proteins in melanocyte lines derived from MART-1 knockout mice, however no mislocalizations were observed. Besides, in primary knockout melanocytes, the processing of Pmel17 was not affected. Nevertheless, electron microscopy studies revealed that MART-1 knockout mice had severe morphological defects in melanosomes of the hair follicle melanocytes. This indicated that the coat color dilution observed in MART-1 knockout mice might be due to the structural defects in the melanosomes, suggesting that MART-1 is required for melanosome biogenesis in the hair follicle.

EPFL2010

Chargement

A MART-1::Cre transgenic line induces recombination in melanocytes and RPE

Iraz Toprak Aydin, Friedrich Beermann

The number of transgenic mouse lines expressing Cre in either type of pigment cells (melanocytes and retinal pigment epithelium, RPE) is limited, and the available lines do not always offer sufficient specificity. In this study, we addressed this issue and we report on the generation of a MART-1::Cre BAC transgenic mouse line, in which the expression of Cre recombinase is controlled by regulatory elements of the pigment cell-specific gene MART-1 (mlana). When MART-1::Cre BAC transgenic mice were bred with the ROSA26-R reporter line, ß-galactosidase expression was observed in RPE from E12.5 onwards, and in melanocyte precursors from E17.5, indicating that the MART-1::Cre line provides Cre recombinase activity in pigment-producing cells rather than in a particular lineage. In addition, breeding of this mouse line to mice carrying a conditional allele of RBP-Jκ corroborated the reported phenotypes in both pigment cell lineages, inducing hair greying and microphthalmia. Our results thus suggest, that the MART-1::Cre line may serve as a novel and useful tool for functional studies in melanocytes and the RPE. © 2011 Wiley-Liss, Inc.

2011

Chargement

Melanoma antigen recognized by T cells 1 (MART-1) is a melanoma-specific antigen, which has been thoroughly studied in the context of immunotherapy against malignant melanoma and which is found only in the pigment cell lineage. However, its exact function and involvement in pigmentation is not clearly understood. Melanoma antigen recognized by T cells 1 has been shown to interact with the melanosomal proteins Pmel17 and OA1. To understand the function of MART-1 in pigmentation, we developed a new knockout mouse model. Mice deficient in MART-1 are viable, but loss of MART-1 leads to a coat color phenotype, with a reduction in total melanin content of the skin and hair. Lack of MART-1 did not affect localization of melanocyte-specific proteins nor maturation of Pmel17. Melanosomes of hair follicle melanocytes in MART-1 knockout mice displayed morphological abnormalities, which were exclusive to stage III and IV melanosomes. In conclusion, our results suggest that MART-1 is a pigmentation gene that is required for melanosome biogenesis and/or maintenance.

2012

Chargement

Analysis of the Pigment Cell Specific Gene MART-1/Melan-A/mlana

Iraz Toprak Aydin

EPFL2010